Drive for wood-pulp grinders and the like



Dec. 16, 1930. w. MERRILL DRIVE FOR WOOD PULP GRINDEiiS AND THE LIKE Filed Feb. 10, 1925 Inventor I I Wilbur L. Mer-r-ill, y

His Attorney.

.latented D UNITED v STATES PATENT OFFICE WILBUR L. MERRILL, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, 'A. CORPORATION 01 NEW YORK I Dawn roa WOOD-PULP enmnnns AND THE LIKE Application filed February In wood ulp grinders ofthe type above 'Fset forth, di

culties are experienced in equalizingthe loads on the respective grinder stones, since the quality of the wood to be ground varies, the area of Wood being ground varies, the grinding surface of the stone varies, and other variables occur which cause the loads represented by the respective stones to vary. From experiencesit may be determined that a certain load on a grinder stone of a given diameter is the most economical from the stand oint of quality, quantity and uniformity of t e pulp which is obtained. It is desirable that this load shall be maintained as nearly as possible during the grinding operation and it is also desirable that the sum of the loads represented by the grinder stones shall be maintained substantially constant.

One of the objects of the invention is to provide a simple and effective arrangement for equalizing the loads on the grinder stones. Another object is to provide a simple and effective arrangement whereby the economical load on each of the grinder stonesv may be maintained as nearly as possibly and the loads on the grinder stones be equalized during normal operations. 1 When one of, a plurality of grinder stones is replaced by a new stone, this new stone will not ordinarily be of the same diameter as the other stone or stones retained and adj ustments aretherefore required in order that the load on this new stone will be the proper value and also in order that the loads on the stones may bear a. predetermined relation to each other. Therefore, a further object of the invention is the provision of a simple and effective arrangement whereby the above conditionmay'be properly taken care of. v

ilt isometimes happens that extreme condi- 10, 1995. Serial No. 8,289.

tions occur in the magazine for the logs,.such as for example, the arching of the logs over one of the stones so that when sufficient wood is ground away, the load on this stone is reduced to a very low value. Since the feeding mechanisms for the various stones are endeavoring to automatically-maintaina constant load on the common grinder motor, the load on the other stone or stones will be in-. creased above a safe value and possibly the feed mechanism broken unless provision is made to take care of this and similar conditions. A still further object of the invention is to provide a simple and effective arrangement for automatically takingv care of conditionssuch as the above so that the load on each grinder stone may be properly regulated regardless of the occurrence of unusual conditions of grinding at the other stone or stones. i

For a better understanding of the invention, reference is had to the accompanying drawing, which shows a very simplified diagram. of a wood pulp grinder drive in accordance with the invention.

Referring to the drawing, the grinder stones 10 and 11- are arranged to be driven by the common grinder motor 12 which is indicated as of the three phase alternating current type, although the invention is not necessarily limited to any particular type of grinder motor. The feeder mechanisms 13 and 14 are rovided for feeding the wood in magazines {hot-shown) to the grinder stones 10 and 11 respectively. The electric feed mo-v tor 15 is provided for operating the feed mechanism 13 and the electric feed motor 16 is provided for operating the feeding mech-. anism 14. These feed motors are energized from a suitable source of supply, and I have indicated these motors as being supplied with current from the generator 17 which is driven by the grinder motor 12. The generator. 17 r provided an automatic regulator for the generator 17 so that the voltage of the generator will be varied in accordance with the load on the grinder motor 12, thereby varying the power supply to the feed motors 15 and 16, and thus in turn varying the loads imposed by the feeding mechanisms 13 and 14 inversely with the load on the grinder motor. In general the arrangement is such that when the load on the grinder motor is increased above the predetermined value, the feeding mechanisms will be operated in such a way that the load imposed by 'the feeding mechanisms on the grinder stones will be decreased, and in case the load on the grinder motor is below the predetermined value, the loads imposed by the feeding mechanisms will be correspondingly increased so as to thereby maintain substantially constant the load on the grinder motor.

An arrangement for effecting this control of the load on the grinder motor is indicated in the drawing. comprises a variable resistance 19 in the circuit of the separately excited generator field 20, and this resistance is varied by means of a regulator under the control of the electromagnet 21 which is energized responsively to the load on the grinder motor 12 by. being supplied with energy from the secondary of the current transformer 22 in one of the supply conductors of the grinder motor. The contact device 23 is biased by means of the spring mechanisms shown in the mid position as indicated in the drawing, and this contact strip is operated by means of the armature 24 associated with the electromagnet 21, through the rods 25 and 26. This regulator is adjusted so as to maintain a predetermined load on the grinder motor by means of the variable resistance 27 which is indicated as being in multiple relation with the winding of the electromagnet 21. The arrangement as shown operates on a function of the cur- -rent in the grinder motor circuit and it is obvious that the regulator maybe arranged to operate on the wattmeter" principlerso as to maintain constant power input in the motor.

In order to insure that the feed motors 15 and 16 will probably distribute the load between them, the armatures of these motors are connected in series relation, as shown, thereby serving to automatically maintain a predetermined relation between the loa'ds'imposed on the grinder stones by the feed mechanisms 13 and 14. These feed motors are indicated as of the series type, and while this is a preferred form of invention, nevertheless the invention is not necessarily limited to the use of series motors for operating the feed mechanisms, since other types of motors may be also employed.

One of the unusual conditions to be taken care of is that of the wood becoming arched As shown, this arrangement and 11.

mechanism or mechanisms will beoperated so as to increase the load on the associated stone or stones so as to thereby maintain substantially constant the load on the grinder motor. The feed mechanism or mecha? nisms for the other stone or stones may be broken in the attempt to keep substantially constant the load on the main grinder motor, and this is one of the unusual conditions which must be taken care of.

In order to-provide for this and similar abnormal conditions, I have provided an arran ement whereby upon the occurrence of suc abnormal conditions, the load to be automatically maintained on the main grinder motor will bequickly reduced. One of the ways in which this may be accomplished is indicated in the drawing, and as shown, comprises the relays 28 and 29 which control the electromagnetic switch 30, which in turn regulates the power supplied by the generator 17 to the feed motors 15 and 16. The electromagnetic switch 30operates to insert the resistor 31 in the supply circuit to the feed motors 15 and 16, and also to insert the section 32 of the resistor 27 so as to permit a greater proportion of the current from the current transformer 22 to'flow through the feed motors 15 and 16 so as to compensate for differences in the diameters of the stones 10 Thus, in case the stone 10 should become worn so that a new stone must be substituted, this new stone will ordinarily be of "compensation must be made for the difference between the stone 10 which was replaced with winding of the electromagnet 21 and thereby IOU the ,new stone. In order to take care'of this and similarvconditions requiring adjustment of the operation of the feed motors, I have provided the adjustablerheostats'33 and 34 for the feed motors 15 and 16, respectively. It will be observed that these'rheostats are arranged so as to shunt the feed motors 15 and 16 respectively, and by varying the value of the rheostats, a very nice adjustment of the loads imposed by the feeding mechanisms 13 and 14 on their respective stones may be had. As thus construetedand arranged and with the. parts 1n their respective positions as started and is running at substantially the shown in the drawings, the operation of my invention is as follows:

Assume that the grinder motor 12 has been normal s eed. When the switch 35 in the circuit 0 the separately excited field 20 of the generator lThas been closed, the feed motors 15 and 16 willbe supplied with power from the generator 17 and by reason of the fact that the field of the generator will take an a'ppreciable time to build up to the value determined by the setting of the contacting strip 23 of the regulator, the loads applied by the feed motors on their respective grinder stones will be gradually built up.

In order to adjust the relation between the loads supplied by the respective feed motors to their grinder stones, either or both of the switches 36 and 37 will be closed and. either the resistance 33 or the resistance 34, or both of these resistances will be adjusted so as to thereby adjust to a great nicety the relationbetween the loads of the feed motors. When this has been done, the resistance 27 will be adjusted by means of the adjusting device indicated so as to adjust the value of load for the grinder motor 12 which is to be automatically maintained by adjusting the resistance 19in the field circuit of the generator 17. It will be assumed that conditions of feeding are substantially normal and that the coils of the relays 28 and 29 are sufliciently energized so that these relays open their. re-

spective contacts. The switch 38 will then be closed, but the closing of this switch will have ho eflect on the operation of the equipment as long as conditions are substantially normal. By reason of the fact that the armatures of the feed motors 15 and 16 are connected in series relation, these feed motors will be controlled the one by the other in such a manner that the predetermined relation between the loads imposed by the feeding mechanisms on their respective grinder stones will be automatically maintained. In case there should be an increase of the load on the grinder motor 12, the arm 24 of the generator field regulator will be attracted under the action of the coil 21 so as to insert a portion of the resistance 19 in the field circuit of the generator, thereby automatically restoring the predetermined load on the grinder motor. It will be obvious thatin case the load on the grinder motor is reduced, the generator field regulator will operate to short-circuit an additional portion of the resistance 19 and thereby eflect an increase of the load on the grinder motor.

In case there should occur some abnormal condition, such as the wood becoming arched over onestone, for example the stone 10, so that when suflicient wood is ground away, the load on this stone is reduced to a very low value, the feed motor 15 will increase in speed very materially so that the voltage rially'less than the voltage drop cross the feed motor 15. The rela 29 will then drop and complete a circuit or the winding of the electromagnetic switch 30. This switch will operate and open the shunt about the resistor 31 in the armature circuit of the feed motors and also open the shunt about the section 32 of the resistance 27. The voltage applied to the feed motors will be very materially reduced and the regulator in the field circuit of the generator will be operated so as to insert a portion of the resistance 19 in the circuit of generator field 20. This will reduce the generator voltage and reduce the load to be automatically maintained on the grinder motor so that the feed mechanisms will not be broken in the attempt to maintain the load on the grinder motor which it is unsafe to maintain due to the occurrence of the abnormal conditions. When the obnormal conditions have ceased to exist, the relay 29 will drop its contacts and thus restore the conditions initially predetermined. The automatic operation of relay 28 and the resulting efi'ect thereof will be apparent from the'foregoing. v

It will be apparent that in case, for example, the stone 10 has become worn, and it is desired to replace this stone with a new stone, either the rheostat 33 or the rheostat 34,01 both of these rheostats, may be adjusted so as to reestablish the predetermined relation between the loads supplied by the feed motors to their respective grinder stones.-

Certain features of the plural feed wood pulpgrinder. system disclosed in this appli cation. are claimed broadly in a .copending application of Weiske and Rupprecht, Serial No. 5,042 filed January 27, 1925, assigned to the same assignee as this application.

In accordance with the provisions of the patent statutes, I have described the principle of operation of my invention, togetherwith the apparatus which I now consider to represent the best embodiment thereof; but I desire to have it understood that the apparatus shown is only illustrative, and that the invention can be carried 'out by other means.

What I claim as new and desire to secure by Letters Patent of the United States, is;

f 1. A wood pulp grinder drive comprising a grinder motor fordriving a plurality of grinder stones, a separate feed motor for feeding the wood to each grinder stone, a generator for supplying power to said feed motors, the said feed motors being connected in seriesrelation to automatically maintain a predetermined relation between the loads imposed on said grinder motor by said feed motors, and means responsive to .the

load on said grinder motor for automatically,

maintain substantially constant the load of said grinder motor.

2. A wood pulp grinder drive comprising a motor for driving a plurality of grinder stones, separate feed mechanism for feeding the wood to each grinder stone, a separate electric motor automatically operated in accordance with the load on the said grinder motor for regulating the speed of said feed mechanisms, and means automatically oper ated in response to a predetermined variation in the loads on the respective feeding mechanisms for controlling the load on the said grinder motor.

3. A wood pulp grinder drive comprising an electric motor for driving a plurality of grinder stones, a separate feed motor for feeding the wood to each grinder stone, a common source of supply for the said feed motors, means operated automatically in accordance with the load onthe said grinder motor for regulating the said source to govern the speed of said feed motors in accordance with the load on the grinder motor, and means operated responsively to a predetermined variation in the speed relation of the said feed motors for regulating the power supplied to the said feed motors from the said source.

4. A wood pulp grinder drive comprising a grinder motor for driving a plurality of grinder stones, a separate feed .motor for feeding the wood to each rinder stone, a generator connected to supp lv power to the said feed motors in series relation, means operated automatically in accordance with the load on said grinder motor for regulating the voltage of said generator to govern the speed of said feed motors in accordance with 'the load on the grinder motor, and electroresponsive means energized responsively to a predetermined variation in the speed relation ofsaid feed motors for reducing the power supplied by said generator to said feed motors.

5. A wood pulp grinder drive comprising a driving motor for a plurality of grinder stones, a separate direct current feed motor for feeding the wood to each grinder stone, a generator having its armature connected to supply power to the armatures of said feed motors in series relation, electroresponsive means energized responsively to the load on said grinder motor for regulating the voltage of said generator, and an electroresponsive device associated with each of said feed motors and controlled thereby, the said devices being connected to selectively respond in accordance with a predetermined variation in the speed relation of said feed motors to reduce the power supplied by said generator to said feed motors.

6. A wood pulp grinder drive comprising a separate direct current feed motor 'for feeding the wood to each of a plurality of grinder motors, means for adjusting the relation between the loads imposed by the said motors on their respective grinder stones, and connections between the said motors for automatically preserving the said adjusted relation between the loads imposed by said motors.

7. In combination in drive for a grinder or the like, a plurality of grinding elements, a motor for driving the same, separate'feed mechanisms associated with each of said elements, a separate electric motor for operating each of said mechanisms, means responsive to the load on said driving motor for automatically regulating the said electric feed motors to automatically maintain a predetermined load on said driving motor, and connections between said feed motors for automatically preserving a predetermined relation between the loads imposed by said feed mechanisms on said elements.

8. In combination, a plurality of grinders, a common driving means therefor, a separate feed mechanism for each grinder, a separate electric motor for operating each of said feed mechanisms, a generator connected to supply power to said feed motors, and a regulator automatically operated in response to the load on said driving means for governing said generator to regulate the aggregate load of the grinders.

9. In combination, a plurality of grinders, a common electric motor for driving said grinders, a separate feed mechanism for each grinder, a separate electric motor for operating each of said feed mechanisms, a generator connected to supply power to said feed motors, and an electroresponsive regulator connected with said grinder motor to respond to the load thereof and connected with 

